A restorer uses a laser on the image of St. Paul in the Catacombs of St. Thecla. (Pontifical Commission for Sacred Archaeology)

Bringing out the big guns — using lasers instead of brushes and trowels — to clean crusty walls and ceilings of Rome catacombs closed to the public, Vatican archaeologists have made what they describe as more “surprising discoveries.”

They haven’t, however, given much information about what those discoveries are. The world will have to wait until next Tuesday, when the Pontifical Commission for Sacred Archaeology holds a press conference at the Basilica of St. Paul Outside the Walls.

The press advisory said that a year after the commission announced the discovery of the “oldest known image of St. Paul” in the catacombs of St. Thecla, the commission will share “further surprising discoveries made by restorers in the ‘cubiculum’ of the same catacombs. Using laser technology, other images of saints have been discovered, likewise the oldest of their kind, on the ceiling of the same area.”

A “cubiculum” is a small room carved out of the rock that served as a chapel or burial chamber.

Last year the commission announced the discovery of a fourth-century portrait of St. Paul in the catacombs close to the basilica, which is named after him. According to tradition, his bones are preserved under the basilica’s main altar.

The image of a bald man with a stern expression, a high forehead, large eyes, distinctive nose and a dark tapered beard tipped experts off that it was St. Paul because it matched images of him from later centuries, the newspaper said.

Image of St. Peter in the Catacombs of St. Thecla. (Pontifical Commission for Sacred Archaeology)

In early June, the Vatican newspaper hinted that the new discoveries would include portraits of other apostles (it already released a photo of a portrait of St. Peter from the same catacomb).

The paper also said the work — including the embracing of new technologies — is a direct result of the re-organization of the pontifical commission under the pontificate of Pope Benedict XVI.